Understanding the interplay between structural and electronic t2g degrees of freedom in perovskites with orbital order-disorder phenomena

While orbital ordering and disordering phenomena have been much studied in oxide perovskites (e.g. colossal magnetoresistance manganites), where the electronic instability is associated with the eg manifold of the TMs, relatively little is known about the phenomena in the fluorides where electronic degrees of freedom associated with t2g electrons are at play. Here we propose a 2-day local structure total scattering study on POLARIS to investigate the orbital disordered ground state in two fluoride transition metal (TM) perovskites NaCoF3 and KFeF3 that are expected to have contrasting Jahn-Teller distortions. Our work will give a broader insight into how orbital ordering phenomena can be systematically tuned, with view to harnessing associated functional properties.